Google + Google Adwords Keyword Tool is great combination that I use most of the time

It lacks longtails sometimes but you can be sure that the search volumes are most accurate from all tools. Why? Because it's from Google and other tools like Wordtracker use meta search engines for their data source.
I use Wordtracker especially for local modifiers.. Lately testing keywordspy, traffic travis, nichebot.
Using Google Adwords Keyword Tool can provide excellent results you just need to know hot to use it. Try different combinations. I first check for couple of sites from that niche in Google KW tool then I drill down deeper. To drill down deeper you have to enter enter each keyword once again for search because Google will show you only 200 keywords at 1 time and it shows the keywords from the top. Also it's good to enter different similar keyword variations in 1 GKWT search. 1 thing can be written in 100 way so you need to come up with all those variations. Also USE GOOGLE. It's so important factor and nobody uses it. All of this 100-200 keywords I get can be Googled and checked in GKWT too get new ideas and variations. In many queries Google will give you suggestions on the bottom of the page. When you start typing your kw in the Google homepage you will see 10 Googles suggestions so Google and check in KW tool each of those.
Of course to see how competitive phrase is use quotes. Up to 5k results it's easy, up to 10k mid hard, up to 30-50k results with quotes is hard but possible. This is flexible and it doesn't have to be like that it's just and estimate and it depends how good are you in SEO and Link Building.
When you make your list of lets say 100 keywords you want to target paste it again in the keyword tool ALL OF THEM, remove the check on synonyms suggestion and check Don't show ideas for new keywords so only your keywords will be displayed. Then put exact matches export to csv for excel then open in excel SUM all the results and you'll see overall search volume if you target them all. To be sure remove top 10 results so you don't contaminate results. I count on 10% of that result to be my search volume if I get to the page 1 for my keywords.
Also you can use Google Adwords Traffic Estimator, just paste all keywords and see how many clicks you will have it usually is the around the amount what I get with 10% of my estimation. And remember Adwords gets 1/5 of organic search volume so there is a chance you get more traffic but Adwords usually have better conversion.
I sometimes work 2-3 days on KW research but I think it's worth because this are the keywords I'll be working on promoting for some time.
Anyway I talk to much. Doesn't matter what tool you are using as long as you are good in what you do
